Many automotive vehicles have both a driver's-side air bag assembly deployably stored within a steering wheel and a front passenger's-side air bag assembly deployably installed in or behind a passenger-side instrument or dash panel. In manufacturing such passenger-side instrument panels, a separate door or other closure is normally provided within a rigid retainer, insert or substrate that forms a portion of the instrument panel. The door serves to conceal and prevent occupants from tampering with the air bag assembly. It is well known to connect such an air bag door to a retainer by using separate fasteners. It is also well known to weaken a section within the door or along one side of the door to allow the door to tear free from its support and pivot into an open position under the force of the inflating air bag. Although arrangements of this sort for connecting the door to a main portion of the retainer permit the door to open and function properly, the use of separate fasteners for joining the door to the retainer increases instrument panel manufacturing and assembly cost. In addition, making the door as a separate part creates an inherent fit and finish problem.
To reduce manufacturing cost and to improve fit and finish, air bag cover assemblies have been developed that do not require separate fasteners to join air bag doors to support structures such as retainers, inserts or substrates. An example of such a system is found in U.S. Pat. No. 5,458,361 issued Oct. 17, 1995 to Gajewski (the Gajewski patent). The Gajewski patent discloses an air bag door that is integrally formed in a like-shaped opening in an insert panel. The door has an outer edge that forms a seam against an inner edge of the insert opening. The door is made of a material that bonds with the insert along at least a portion of the seam. There is also a mechanical interlock between the door and the insert along at least a portion of the seam. The mechanical interlock comprises interlocking dovetails extending integrally outward from the door outer edge and integrally inward from the insert opening inner edge. In one embodiment, the dovetailed mechanical interlock serves as a hinge when the door is forced open by air bag inflation. The configuration of the dovetailed mechanical interlock resists outward movement of the door, but does not resist inward movement of the door relative to the insert. In other words, if there was no adhesive bond between door and insert the mechanical interlock would not support the door in the insert against inwardly directed forces.
The Gajewski insert and door are formed by first injecting molten insert material into a mold cavity. As the insert material is being injected, the area to be injected with door material is partitioned by retractable divider blades, some of which also serve to form dovetails along a portion of the inner edge of the insert opening. Once the insert material has hardened, the divider blades are retracted to expose the inner edge of the insert opening and the insert dovetails. Door material is then injected into the mold cavity in the region that the blades had previously partitioned. The door material adheres to the inner edges of the insert opening forming a butt joint. The door material also flows around the insert dovetails to form mechanically interlocked door dovetails. Exterior class A surfaces, i.e. surfaces visible to vehicle occupants, of the Gajewski door and insert lie flush with one another. However, the interior surfaces of the Gajewski door and insert are interrupted by a protrusion extending integrally inward from along the mechanically interlocked regions of the seam. The Gajewski patent is assigned to the assignee of the present invention and is incorporated herein by reference.
U.S. Pat. No. 5,590,901 issued Jan. 7, 1997 to MacGregor (the MacGregor patent) also discloses a method of making a retainer or substrate with an integral door. However, unlike the Gajewski patent, an air bag door and trim panel substrate are formed separately and then the door is inserted and adhesively bonded to the substrate.
What is needed is a retainer having an integral air bag door that is removably held in place in an air bag deployment opening in the retainer by simple non-adhesive means and without using separate fasteners to join door to retainer. What is also needed is simple method for making such a door.